The present invention relates broadly to communications cable and more particularly, to communications cable containing at least one twisted pair of insulated conductors.
Insulated conductors such as those used in communications cable are often provided as twisted pairs of insulated conductors having two insulated conductors twisted about each other to form a two conductor group. A typical assembly for these communications cables comprises two or more twisted pairs of insulated conductors bundled together and contained in a cable jacket. This assembly can facilitate the installation of the cable. In addition, the cable can be connected to other cable components by stripping the cable jacket and making the proper connections between the insulated conductors.
One problem associated with communications cable produced with the conventional twisted pair assembly is that crosstalk can occur between twisted pairs of insulated conductors that can negatively affect the signals transmitted by these conductors. Crosstalk may especially present a problem in high frequency applications because crosstalk may increase logarithmically as the frequency of the transmission increases. Because crosstalk is affected to some degree by the distance between twisted pairs of insulated conductors, one method of reducing its occurrence is to space the twisted pairs of insulated conductors apart using a spacing means. An example of such spacing means can be found in U.S. Pat. No. 5,789,711 to Gaeris et al. which discloses a high performance data cable which has an interior support or star separator. Another example of such a spacing means can be found in U.S. Pat. No. 5,969,295 to the present inventor Boucino, et al., (xe2x80x9cthe ""295 patentxe2x80x9d) which discloses a communications cable that includes a cable jacket, twisted pairs of insulated conductors, and a spacer separating the twisted pairs of insulated conductors. The spacer in the ""295 patent extends within the cable jacket and has a longitudinally extending center portion and a plurality of wall portions radiating from the center portion thereby defining a plurality of compartments within the cable jacket.
According to embodiments of the present invention, communications cables are provided which utilize a cable jacket, twisted pairs of insulated conductors, and a spacer separating the twisted pairs of insulated conductors. The spacer extends within the cable jacket and has a longitudinally extending center portion and a plurality of wall portions radiating from the center portion thereby defining a plurality of compartments within the cable jacket. In various embodiments of the present invention, the plurality of wall portions include a plurality of radiating sections with varying geometric shapes. The twisted pairs of insulated conductors are disposed in the compartments.
In embodiments of the present invention, communications cables include a cable jacket, a spacer extending within the cable jacket and having a longitudinally extending center portion and plurality of longitudinally extending wall portions radiating from the center portion that increase in thickness from the center portion to the cable jacket. The spacer and the cable jacket define a plurality of compartments within the cable jacket. One or more twisted pairs of insulated conductors are disposed in one or more of the plurality of compartments. The communications cable may also have a shield extending between the spacer and the cable jacket. The twisted pairs of insulated conductors may each have a different lay length. The plurality of longitudinally extending wall portions may be configured so as to define a plurality of compartments of a helical configuration within the cable jacket and the plurality of twisted pairs of insulated conductors located within the plurality of compartments may extend helically about the longitudinal axis of the cable.
In other embodiments of the present invention, the plurality of longitudinally extending wall portions may increase in thickness over only a portion thereof from the center portion to the cable jacket.
In further embodiments of the present invention, the plurality of longitudinally extending wall portions may decrease in thickness over only a portion thereof from the center portion to the cable jacket.
In still further embodiments of the present invention, the longitudinally extending wall portions have a first radial section that increases in thickness with distance from the center portion and a second radial section that decreases in thickness with distance from the center portion. The first radial section may be located between the center portion and the second radial section or the second radial section be may located between the center portion and the first radial section. The first radial section and the second radial section may be configured such that the plurality of longitudinally extending wall portions have a convex shaped cross-section that may be arcuate and/or include a plurality of faces. The first radial section and the second radial section may also be configured such that the plurality of longitudinally extending wall portions have a concave shaped cross-section that may be arcuate and/or include a plurality of faces. The first radial section and second radial section may further be configured such that the plurality of longitudinally extending wall portions have a recessed portion and/or a ribbed portion.
In still other embodiments of the present invention, the longitudinally extending wall portions may have a first section having a first thickness, a second section having a second thickness and a third section having a third thickness and located between the first section and the second section. The third thickness is different from the first and second thickness. In one embodiment, the first thickness, the second thickness and the thickness of the third section are all different. In another embodiment, the first thickness and the second thickness may be the same and the third thickness may be either thicker or thinner than the first thickness.
In still further embodiments of the present invention, the longitudinally extending wall portions may have a sawtooth shaped cross-section having a plurality of teeth. Each tooth may have a tooth height and a tooth spacing. In one embodiment, each tooth height is the same. In other embodiments, at least two tooth heights are different. In yet other embodiments, each tooth spacing is the same. In still other embodiments, at least two tooth spacings are different. In other embodiments, at least two tooth heights are different and at least two tooth spacings are different.
In still other embodiments of the present invention, the longitudinally extending wall portions may have a first radial section and a second radial section having a knob shaped cross-section. The knob shaped cross-section may be any portion of a knob including a half knob and/or a whole knob.